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📜  Java 8-功能接口

📅  最后修改于: 2021-01-05 04:38:53             🧑  作者: Mango

功能接口具有单个功能。例如，具有单个方法“ compareTo”的Comparable接口用于比较目的。 Java 8定义了许多在lambda表达式中广泛使用的功能接口。以下是java.util.Function包中定义的功能接口的列表。

Sr.No. Interface & Description
1

BiConsumer

Represents an operation that accepts two input arguments, and returns no result.
2

BiFunction

Represents a function that accepts two arguments and produces a result.
3

BinaryOperator

Represents an operation upon two operands of the same type, producing a result of the same type as the operands.
4

BiPredicate

Represents a predicate (Boolean-valued function) of two arguments.
5

BooleanSupplier

Represents a supplier of Boolean-valued results.
6

Consumer

Represents an operation that accepts a single input argument and returns no result.
7

DoubleBinaryOperator

Represents an operation upon two double-valued operands and producing a double-valued result.
8

DoubleConsumer

Represents an operation that accepts a single double-valued argument and returns no result.
9

DoubleFunction

Represents a function that accepts a double-valued argument and produces a result.
10

DoublePredicate

Represents a predicate (Boolean-valued function) of one double-valued argument.
11

DoubleSupplier

Represents a supplier of double-valued results.
12

DoubleToIntFunction

Represents a function that accepts a double-valued argument and produces an int-valued result.
13

DoubleToLongFunction

Represents a function that accepts a double-valued argument and produces a long-valued result.
14

DoubleUnaryOperator

Represents an operation on a single double-valued operand that produces a double-valued result.
15

Function

Represents a function that accepts one argument and produces a result.
16

IntBinaryOperator

Represents an operation upon two int-valued operands and produces an int-valued result.
17

IntConsumer

Represents an operation that accepts a single int-valued argument and returns no result.
18

IntFunction

Represents a function that accepts an int-valued argument and produces a result.
19

IntPredicate

Represents a predicate (Boolean-valued function) of one int-valued argument.
20

IntSupplier

Represents a supplier of int-valued results.
21

IntToDoubleFunction

Represents a function that accepts an int-valued argument and produces a double-valued result.
22

IntToLongFunction

Represents a function that accepts an int-valued argument and produces a long-valued result.
23

IntUnaryOperator

Represents an operation on a single int-valued operand that produces an int-valued result.
24

LongBinaryOperator

Represents an operation upon two long-valued operands and produces a long-valued result.
25

LongConsumer

Represents an operation that accepts a single long-valued argument and returns no result.
26

LongFunction

Represents a function that accepts a long-valued argument and produces a result.
27

LongPredicate

Represents a predicate (Boolean-valued function) of one long-valued argument.
28

LongSupplier

Represents a supplier of long-valued results.
29

LongToDoubleFunction

Represents a function that accepts a long-valued argument and produces a double-valued result.
30

LongToIntFunction

Represents a function that accepts a long-valued argument and produces an int-valued result.
31

LongUnaryOperator

Represents an operation on a single long-valued operand that produces a long-valued result.
32

ObjDoubleConsumer

Represents an operation that accepts an object-valued and a double-valued argument, and returns no result.
33

ObjIntConsumer

Represents an operation that accepts an object-valued and an int-valued argument, and returns no result.
34

ObjLongConsumer

Represents an operation that accepts an object-valued and a long-valued argument, and returns no result.
35

Predicate

Represents a predicate (Boolean-valued function) of one argument.
36

Supplier

Represents a supplier of results.
37

ToDoubleBiFunction

Represents a function that accepts two arguments and produces a double-valued result.
38

ToDoubleFunction

Represents a function that produces a double-valued result.
39

ToIntBiFunction

Represents a function that accepts two arguments and produces an int-valued result.
40

ToIntFunction

Represents a function that produces an int-valued result.
41

ToLongBiFunction

Represents a function that accepts two arguments and produces a long-valued result.
42

ToLongFunction

Represents a function that produces a long-valued result.
43

UnaryOperator

Represents an operation on a single operand that produces a result of the same type as its operand.

功能接口示例

谓词接口是一个函数接口，带有方法test(Object)来返回布尔值。此接口表示已测试对象为真或假。

使用您选择的任何编辑器(例如，C：\> JAVA)创建以下Java程序。

Java8Tester.java

现场演示
import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;

public class Java8Tester {

   public static void main(String args[]) {
      List list = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8, 9);
        
      // Predicate predicate = n -> true
      // n is passed as parameter to test method of Predicate interface
      // test method will always return true no matter what value n has.
        
      System.out.println("Print all numbers:");
        
      //pass n as parameter
      eval(list, n->true);
        
      // Predicate predicate1 = n -> n%2 == 0
      // n is passed as parameter to test method of Predicate interface
      // test method will return true if n%2 comes to be zero
        
      System.out.println("Print even numbers:");
      eval(list, n-> n%2 == 0 );
        
      // Predicate predicate2 = n -> n > 3
      // n is passed as parameter to test method of Predicate interface
      // test method will return true if n is greater than 3.
        
      System.out.println("Print numbers greater than 3:");
      eval(list, n-> n > 3 );
   }
    
   public static void eval(List list, Predicate predicate) {

      for(Integer n: list) {

         if(predicate.test(n)) {
            System.out.println(n + " ");
         }
      }
   }
}

在这里，我们传递了Predicate接口，该接口接受单个输入并返回Boolean。

验证结果

使用javac编译器编译类，如下所示：

C:\JAVA>javac Java8Tester.java

现在如下运行Java8Tester-

C:\JAVA>java Java8Tester

它应该产生以下输出-

Print all numbers:
1
2
3
4
5
6
7
8
9
Print even numbers:
2
4
6
8
Print numbers greater than 3:
4
5
6
7
8
9